The Lure of Forbidden Food

In an experiment, researchers at Pennsylvania State University gave preschool children the opportunity to “work” for a food reward. All the child had to do was click a computer mouse four times to earn a cinnamon-flavored graham cracker.

But earning additional treats required progressively more effort. A second treat required eight clicks. Then 16. Then 32.

Some children were satisfied after one cracker, while others kept clicking for a few additional crackers. Most of the preschoolers were done after about 15 minutes, but some children stayed with it, accumulating as many as 2,000 clicks before the researchers ended the task after 30 minutes.

Children who are highly motivated by food — researchers have called them “reactive eaters” — are of particular interest to childhood health experts. Were they born this way? Or do parents create reactive eaters by imposing too many food rules and imposing restrictive eating practices at home?

The answer is probably a little bit of both. Genetics and biology play a role in the foods we like and the amounts we tend to eat. At the same time, studies show that children who grow up in homes with restrictive food rules, where a parent is constantly dieting or desirable foods are forbidden or placed out of reach, often develop stronger reactions to food and want more of it when the opportunity presents itself.

In the Penn State experiments, the same preschoolers who worked for food were later offered two types of graham crackers (Scooby-Doo or SpongeBob SquarePants) during their snack time. On five occasions, one type of graham cracker treat was freely available, while the other was placed in a glass bowl with a lid and put off limits. The restricted snacks were available for only five minutes of snack time.

Not surprisingly, the graham crackers that were off limits were enticing to all the preschoolers. But the children who had worked hardest in the clicking task — the “reactive” ones — also had the strongest response to the forbidden food.

“The message is that restriction is counterproductive — it just doesn’t work very well,” said Brandi Rollins, a Penn State postdoctoral researcher and lead author of the study, which was published in February in the journal Appetite. “Restriction just increases a child’s focus and intake of the food that the parent is trying to restrict.”

Leann Birch, senior author of the Penn State studies and now food and nutrition professor at the University of Georgia, said additional research has shown that parents who impose highly restrictive food rules, such as putting desirable foods out of reach, tend to have children who are the most reactive to food in the laboratory.

“It’s hard to talk cause-and-effect,” said Dr. Birch. “The parents are responding to kids’ reactivity, and the child is reacting to the parenting and to a general genetic predisposition. The only way to break the cycle is to try to get the parents to respond differently.”

While restrictive feeding practices can backfire, that doesn’t mean children should have unfettered access to all foods. Instead, parents should be aware that tight control over food can set off overeating in some children. The solution is to control the quality of the food in the home.

Don’t buy soda, candy and chips and place them off limits on the top shelf of the pantry. Stock the house with healthful foods, and then allow children access and a reasonable amount of control over what they eat. At snack time, for instance, give them a choice between an apple or orange or vegetables with different dips.

The primary food rule should be “a high quality diet for all,” said Dr. David Ludwig, director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital.

Parents should not have different rules for themselves, or allow a thin child to eat junk food freely and restrict a sibling with a weight issue. Parents typically don’t have to worry about an overweight child overeating when they are serving high-quality unprocessed foods. For instance, it’s almost impossible to binge on apples. But process the apple into applesauce or juice, and it becomes a junk food that is easy to overeat.

Occasional treats outside the home are fine. “Take the kid out for ice cream once or twice a week, but don’t keep it in the house,” Dr. Birch said. Dr. Ludwig noted that with young children, parents needed to set more limits. But adolescents should be given more freedom to eat.

“I don’t like the concept of telling a hungry child you can’t eat,” said Dr. Ludwig. “Ultimately, we want children to gain better connection to their inner satiety cues. So if their body is telling them they are hungry, don’t ignore that — just pay close attention to the quality of the foods that are offered.”